I am not an expert in any way nor do I follow the media hype but I think Beyonce did lip-sync the national anthem at Obama's inauguration. It is quite clear to even a person of not much experience in singing or lip-sync in that matter. Honestly it is also a bit disrespectful and embarrassing
When rumors started going around that Beyoncé had lip synced the national anthem, nobody really came forward to dispute those rumors and shortly after, they were confirmed to be true. So yes, Beyoncé did lip sync, but she also pre-recorded her own vocals so while she wasn't singing live, it was her voice being heard.
Sources at the inauguration have confirmed that Beyonce faked her performance. USMC spokeswoman claimed that Beyonce had originally wanted to sing live, but at the last second switched to pre-recorded music. Plus, from the actual video you can tell she was lip syncing. While there is nothing wrong with lip syncing as long as you give a good performance, there is no reason to hide it. But it is obvious she did.
I believe Beyonce was lip-syncing during the Obama inauguration. When I first watched her sing I did not notice but I saw people on Twitter claiming that she was not really singing. I went back to watch it again and it really looks like she was lip-syncing during her performance.